It is provided a compound of formula (I′); wherein R5 is selected from the group consisting of —H, —OM, —COOM, —NH2, —SO3M, (C1-C4)alkyl, and halogen; and A is a radical having at least 3 C atoms selected from the group consisting of: i) a radical of formula (i) wherein R7 is selected from the group consisting of —OM, and —COOM, and n is 0, 1 or 2; and ii) a radical of formula (ii) or of formula (iii) wherein R8 is selected from the group consisting of —H, (C1-C4)alkyl; and wherein M is independently selected from the group consisting of H, an alkaly metal, and NH4+. It is also provided a process for the preparation thereof, a composition comprising it, and its use for correcting deficiencies of metals in plants.